My 19f gf keeps changing how she feels about our poly relationship I’m 18m seeking advice

Hi I’m looking for advice one how to handle my poly relationship with my gf so for some back story me 18m and my 19f are in a poly relationship and rules an boundaries keeps getting changed for example before we started this poly relationship it was made clear that I would be the main partner and she would be my main partner she has now saying her new partner who she just started seeing less then a week ago is allowed to tell what I can and can’t do with my gf that would make him uncomfortable and she is claiming we are equals is there a way to explain in my head we are not and will never be equal so Reddit any advice? this is main and her first poly relationship to emphasize I am looking for advice on how to approach this situation any helps thank you Tldr need advice on how navigate a poly relationship? Sorry for the lack of grammar it’s late and on mobile